Ok, it is working for me too on 3.6.8!
I use the MODDED version of this Mod that KURTZ posted on reply nr
895 as ADMINS are NOT affected by the Mod!
BUT...! (there is always a 'but'...!)
There is this MAIN problem for international users (I run a portuguese board)
One of the MOST IMPORTANT phrases on this Mod has no capabilities for translation inside vBulletin Phrasing system:
If you are running an international board (and you need to translate into your own language) just open the file:
"product-xenon_prevdoublepost.xml"
or
"product-xenon_prevdoublepost_modded.xml"
BEFORE you install this mod and TRANSLATE the following text (bolded) into your language:
------- original piece of code to TRANSLATE -------
$doublepost['message'] = $doublepost['pagetext'] . "\n\n[SIZE=\"1\"][COLOR=\"Silver\"]" . $vbulletin->userinfo['username'] . '
added ' . intval((TIMENOW - $doublepost['dateline'])/60) . '
Minutes and ' . ((TIMENOW - $doublepost['dateline']) % 60). '
Seconds later...' . $vbulletin->options['xen_dp_spacer'] . "[/color][/size]\n\n" . $post['message'];
------- /original piece of code to TRANSLATE -------
Hope it helps!